The problem in your case is that you’ve now included NNFS.jl in two different places–once inside Layers.jl and again in your main file. Those separate include()s have created two completely unrelated modules which happen to have the same name. That’s why it’s important not to include the same file multiple times. Here’s a post with a similar question on avoiding multiple includes that you might find helpful: Need to include one file multiple times, how to avoid warning - #5 by rdeits
In your case, you should be able to replace:
include("NNFS.jl")
import .NNFS: forward
with
import ..NNFS: forward
in Layers.jl